This program has been directed to development of assisted breeding techniques for the chimpanzee and other nonhuman primates. Methods for collection and cryostorage of semen have been established and fertility of stored sperm demonstrated. In vitro fertilization of chimpanzee oocytes is routine, there has been no term pregnancy in the chimpanzee after IVF, although we have identified three chemical pregnancies. However, we believe we have identified a potential reason for this situation, which has to do with the characteristics of the menstrual cycle used for reimplantation of the embryos. Thus, we have correlated an increase in Al success with the pattern of the menstrual cycle endocrine changes such that in the optimum cycle, Al success rate is over 80% for a single insemination, as opposed to around 20% for unselected cycles. That change is hypothesized to relate to endometrial development and the success of implantation. As a result of the present moratoriu m on chim panzee breeding, we have cryobanked chimpanzee embryos at the 8 - 16 cell stage for future use rather than immediately using them for reimplantation. FUNDING NIH / RR03587-1151 $207,223 4/01/93 - 8/31/98 PUBLICATIONS Gould, K.G. and Younis, A.I Potential use of fish antifreeze proteins in primate sperm cryopreservation. Cryobiology (In press). Younis, A.I., Rooks, B., Khan, S. and Gould, K.G. The effects of antifreeze peptide III (AFP) in insulin transferrin selenium (ITS) on cryopreservation of chimpanzee (Pan troglodytes) spermatozoa. J. Androl. 19:207-214, 1998. P51RR00165-38 1/1/98 - 12/31/98 Yerkes Regional Primate Research Center